docstr: Test a SavedModel that fails due to an invalid signature_key.
docstr_tok: ["Test","a","SavedModel","that","fails","due","to","an","invalid","signature_key","."]
code: def testSimpleSavedModelWithInvalidSignatureKey(self):
      """Test a SavedModel that fails due to an invalid signature_key."""
      saved_model_dir = self._createSimpleSavedModel(
          shape=[1, 16, 16, 3]
      )
      with self.assertRaises(ValueError) as error:
          self._convertSavedModel(
              saved_model_dir, signature_key="invalid-key"
          )
      self.assertEqual(
          "No 'invalid-key' in the SavedModel's SignatureDefs. "
          "Possible values are 'serving_default'.",
          str(error.exception),
      )
  
imports: import os
  from tensorflow.lite.python import convert_saved_model
  from tensorflow.python.client import session
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.platform import test
  from tensorflow.python.saved_model import saved_model
  from tensorflow.python.saved_model import signature_constants
  from tensorflow.python.saved_model import tag_constants
label_desc: Use image node_id 8 for calling the FreezeSavedModelTest obj's underlying member method code with example usage: obj.testSimpleSavedModelWithInvalidSignatureKey() without return types